sysconf adding few more constants. #4053
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src/shims/unix/foreign_items.rs
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| // the machine's fd table does not start with a pre-allocated size but just the | ||
| // standard streams so we can't use it here and the spec imposes | ||
| // a minimum of `_POSIX_OPEN_MAX` (20). | ||
| ("_SC_OPEN_MAX", |this| Scalar::from_int(20, this.pointer_size())), |
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20 seems really really low here. Why would we report such a low limit?
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I can set to 1024 (what linux returns) some other platforms return higher values. wdyt ?
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Isn't it dynamic on Linux, determined by ulimit?
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1024 being the max here indeed. but then 20 is too low for you so what do you propose ?
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The ulimit for FDs can easily be much higher, like 64k.
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on illumos it s 65536 ; on my debian it is only 1024 by default with unlimited but as root I can push it higher indeed.
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But I guess 1024 is not an unreasonable value. The comment should make it clear that this is completely arbitrary and we can adjust if it that turns out to be helpful.
src/shims/unix/foreign_items.rs
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| // a minimum of `_POSIX_OPEN_MAX` (20). | ||
| ("_SC_OPEN_MAX", |this| Scalar::from_int(20, this.pointer_size())), | ||
| // The spec imposes a minimum of `_POSIX_ARG_MAX` (4096). | ||
| ("_SC_ARG_MAX", |this| Scalar::from_int(4096, this.pointer_size())), |
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We don't support exec anyway so I don't think there's any point in supporting this constant.
src/shims/unix/foreign_items.rs
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| // The spec imposes a minimum of `_POSIX_ARG_MAX` (4096). | ||
| ("_SC_ARG_MAX", |this| Scalar::from_int(4096, this.pointer_size())), | ||
| // The spec imposes a minimum of `_POSIX_CHILD_MAX` (25). | ||
| ("_SC_CHILD_MAX", |this| Scalar::from_int(25, this.pointer_size())), |
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We don't support process spawning so it seems pointless to support this.
src/shims/unix/foreign_items.rs
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| // The spec imposes a minimum of `_POSIX_CHILD_MAX` (25). | ||
| ("_SC_CHILD_MAX", |this| Scalar::from_int(25, this.pointer_size())), | ||
| // 16 here is the least common denominator (i.e. macos, solarish). | ||
| ("_SC_NGROUPS_MAX", |this| Scalar::from_int(16, this.pointer_size())), |
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Not sure how this is going to be helpful for any program Miri supports?
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that was just "anticipation" I planned try to use the value for this line instead of the hardcoded 1 to see if this help ; not urgent tough.
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net is anyway not supported by Miri, so seems a bit premature to add that constant already.
devnexen
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RalfJung
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e.g. _SC_NGROUPS_MAX can be useful for socket ancillary data.